The presentation today on GPC and HPLC reminded me of a Baran Lab blog post I read not too long ago about moving bed chromatography and this paper specifically.
This type of chromatography was developed to better separate enantiomers by moving the stationary phase of a column in the opposite direction of the mobile phase as shown in the diagram below.
It's tough to move the stationary phase though without causing mixing and other problems and so they designed a simulated moving bed system. This is comprised of four sections of regular columns with various ports for feeding and extracting solvent in and out of. By rotating the ports at which you feed mobile phase into and extract products in the direction with the mobile phase flow, you simulate the solid moving in the opposite direction. This process is widely used in industry, the separation of fructose being a notable example.
Of course this requires tons of optimization which you can read about in that paper.